The purpose of this research is to develop instrumentation for continuously monitoring by non-invasive means the intracranial pressure (ICP) of neurosurgical patients in intensive care. The technique selected makes use of a passive pressure transensor which is implanted extradurally in a burr hole made in the skull. By means of radio frequency coupling, an external interragator determines the pressure sensed by the implanted transensor. A number of intracranial pressure monitors have been built using this technique. At the present stage of the monitor development an individual must be present to make the intracranial pressure determinations. The monitor has been tested and evaluated with animals and has aided in the course of treatment of a few patients. A clinical evaluation will soon be conducted using a larger number of neurosurgical patients. The objectives of this research proposal are: 1) The development and evaluation of a bed-side monitor to make possible the 24 hour recording of ICP with provision for alarm when the ICP is excessively high or when pathological ICP wave patterns exist, 2) The further development of the transensor design to improve accuracy, stability, and reliability, and 3) The detailed study of the accumulated ICP data in terms of ICP dynamics and CSF physiology.